Preface to Third Edition
PEARL HARBOR and all its consequences have come since this Primer's first birthday. Thousands of officer candidates have taken up with grim determination the study which to me for years has been a delightful hobby.
In preparing a new edition, the chief problem was whether to cut to the bone and leave only the bare essentials for practical purposes or to retain what seemed, and still seems to me, essential for a secure understanding of the subject.
Pruned down to lines of position only and plotting on charts or plotting sheets, it is possible to get along without the following:
Meridian altitudes, reductions to the meridian and ex-meridian sights for latitude, interval to noon, time of transit, time of sun on the prime vertical, time-sights for longitude, sights for determination of chronometer error, trigonometry, logarithms, much of the sailings, basic astronomy, and sidereal time. (I realize one need not even know the meaning of declination in order to use the almanac andH. 0.214 effectively.)
The original purpose of the Primer however was to help clarify obscurities. It seems to me this can best be done by a build-up from simple to complex, and by giving some procedures which, though no longer needed, have been strong links in the chain leading to present practice. So the main framework of this book remains unchanged.
Some omissions and many more additions will, I hope increase usefulness. While written primarily for surface work, the principles here given are, of course, basic for aerial navigation. No attempt is made to supply detail for the latter, which is so adequately covered in Dutton.
I am still convinced that years of custom have made it more natural and easy to look, in imagination, at this world and the universe from above the north rather than from below the south pole. Hence I have retained the style of diagram in general use until the years 1936-39, when the leading texts shifted their viewpoint to face Antarctica. Probably the important thing is to get the habit of using some time diagram — not a particular type.
In this third edition, about twenty-five minor corrections, changes or insertions have been made without change of page number. An important addition on Sidereal Time has been added on page 249 and the author's new "Uniform Method for More Exact Time of Local Transit of Any Body" will be found on pages 254-258.
Having been found physically ineligible for active duty, I launch this new Primer with a bold hope that somehow its influence, however small, will count in the score of ultimate Victory.
J. F. February, 1944 Chicago, Illinois